Bearings are used in a wide variety of applications. Representative example applications include simple door hinges, internal combustion engines, heavy duty construction equipment, and other applications that may subject a bearing to corrosive materials, abrasive particles, or non-lubricated environments. In these applications and others, bearings support contact forces between connected objects while allowing the objects to move relative to one another, either through linear motion, rotational motion, or a combination thereof.
Wear is the degradation that can occur to a bearing through extended use. Wear is often caused by an increase in friction, which is the resistance to relative motion between objects. Some causes of friction contributing to wear include loose particles plowing (e.g. cutting) into the bearing and asperity (e.g., surface irregularities) interactions at the surfaces of the bearing.
Prior art bearings address plowing by providing one surface much softer than the surface it contacts. In this respect, a majority of plowing takes place in the softer material, resulting in less energy consumption and therefore less friction than would otherwise occur when employing relatively hard materials. Employing softer material may also allow a loose particle to be embedded into the softer surface and therefore be substantially removed from the interface between the surfaces. This also has the effect of reducing friction because the particle no longer interacts at the bearing surfaces. Prior art bearings also reduce plowing by introducing particle traps that reduce the amount of particles between bearing surfaces by allowing the particles to collect away from the bearing surface.
Asperity interactions have been addressed in the prior art. For example, by improving bearing surface finishes, the amount and severity of asperity interactions is reduced.
Plowing or asperity interactions are not as problematic for some types of bearings. For instance, plowing and asperity interactions are less of a concern for hydrodynamic bearings which do not normally make direct contact with each other during operation.